Process for producing composite filaments

ABSTRACT

A FILAMENT MATERIAL COMPRISES A CORE CONSISTING OF A SUBSTANTIALLY HOMOGENEOUS POLYMER MATERIAL (A) AND A COAT CONSISTING OF TWO MUTUALLY INCOMPATIBLE POLYMER MATERIALS (B) AND (C) WHERE (B) IS COMPATIBLE WITH (A) AND FORM A SUBSTANTIALLY HELICAL FIBROUS STRUCTURE ON THE SURFACE OF (A) AND (C) IS EASILY REMOVABLE. TO MAKE THE FILAMENT MATERIAL, A DISPERSION OF (B) AND (C) IS   APPLIED TO THE SURFACE OF (A) WHILE THIS IS BEING EXTRUDED WHEREAFTER THE EXTRUDED STRAND IS SUBJECTED TO STRETCHING AND TWISTING.

March 21, 1972 oLE-BENDT RAsMussEN 3,651,195

PROCESS FOR PRODUCING COMPOSITE FILAMENT Filed May 29, 1968 ;U.s.,cl.A2154-171 .K

United States Patent O Y Y 3,651,195 lPROCESS FOR PRODUCING COMPOSITEFILAMENTS Ole-Bendt Rasmussen, 7 Topstykket, 3460'Birkerod, DenmarkFiled May 29, 1968, Ser. No. 733,990 Claims priority, application GreatBritain, May 30, 1967, 24,836/ 67 Int. Cl. B29f 3/10 9 Claims ABSTRACTOF THE DISCLOSURE A filament material comprises a core consisting of asubstantially homogeneous polymer material (A) and a coat consisting oftwo mutually incompatible polymer materials (B) and (C) where (B) iscompatible with (A) and form a substantially helical fibrous structureon the surface of (A) and (C) is easily removable. To make the filamentmaterial, a dispersion of (B) and (C) is applied to the surface of (A)while this is being extruded whereafter the extruded strand is subjectedto stretching and twisting.

BACKGROUND OF THE INVENTION The present invention relates to a compositefilament material capable of forming a textile yarn by removal of aprotective polymer contained therein.

It is known that polymer/polymer dispersions which have been effectively-stretched before solidification form a yarn-like structure when one ofthe polymers is removed by dissolving. The said known yarn-likestructure generally has the character of being a stretched sponge ornetwork.

In experiments preceding the present invention it was found that theindividual fibres of such yarn could be produced in a surprisingfnene-ss hereby yielding an extremely soft and fluffy yarn having ahigher total surface area, improved dyeability and improved ability fortransport of moisture. These improvements were in particular found whena relatively high amount of protective polymer was admixed and againremoved. However, the above advantages Were obtained at the expense oftensile strength.

SUMMARY OF THE INVENTION The filament according to the present inventioncomprises, as core material, a substantially homogeneous polymermaterial (A) and, as a coat, a fine dispersion in stretched state of atleast two mutually incompatible polymer materials (B) and (C), (B) beingcompatible with (A) and at the interphase between the coat and the corebeing in adhesive connection with the latter, (C) being easilyremovable, (B) forming a fibrous structure having an average fibrediameter about or below 10p, the fibres on the average being arrangedaround the core according to a helical orientation.

The said filament or removal of the protective polymer yields a yarnhaving at its surface the above-mentioned improved properties, andgetting from its core part, where such properties are of lessimportance, a tensile strength almost at the same level as that of amonofilament. The surface part and the core part will be in relativelystrong connection partly because of the above-mentioned compatibility,and partly because of the helical arrangement of the orientation, theabrasion resistance of the yarn thus being suitable. The structureaccording to the invention thus presents a surprising combination ofdesirable yarn properties.

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The word compatibility as used above is to indicate a mutual solubilitybeing sufficient for the formation of an adhesive bond. The expressionon the average being arranged around the core according to a helicalorientation is to indicate that the meshes of the said network or spongemay be strongly opened, although on the average the said fibres follow ahelical orientation. The word orientation is not meant to indicate anyorientation of molecules which will be optional, but indicates thearrangement of the direction of the fibre.

The components B and C are preferably selected in such a manner that Bwill be in the form of crystal whiskers in the filament according to theinvention. Suitable conditions for producing oriented polymer whiskersfor use in connection with yarn production appear in my copendingapplication S.N. 528,916, now U.S. Pat. No. 3,499,822 issued Mar. 10,1970. Such Iwhiskers as disclosed in the said patent are normallymutually connected through intercrystalline links having crossdimensions far below l/i. The said structure is advantageous in thepresent invention, as the whiskers are relatively regular and inrelatively good adhesive connection through the said links.

In a preferred embodiment of the present invention, the said component Bhas a higher melting point or melting range than component A. Duringextrusion of the composite structure according to the invention, B willthlus solidify while A will sti-ll be elongated in fluid state, theresult being that the relatively solid Ifibrous B material will split-upduring the drawing-down of the core material A. The said splitting upincreases the fluiness of the surface material formed when theprotective (C) has been removed.

In another embodiment of the present invention, B has a higher module ofelasticity than A. The said selection is based on the observation thatthe best results are obtained when the surface consists of fibres beingextremely fine and simultaneously stiff, that however the core havingmuch bigger diameter than the libres at the surface, preferably shouldbe made from a substantially softer polymer. Thus, the core may withadvantage be produced from an elastomer.

In order to obtain the above-mentioned combinations of properties in thecore and surface, the polymer A may with advantage be selected as acopolymer containing a high amount of the segments from which B isformed.

The invention also provides a suitable process for producing a compositefilament material of the character re ferred to. According to theinvention said process comprises the steps of extruding a continuousstrand of a filament forming polymer material (A), applying to thesurface of said strand, while this is being extruded, a coating materialconsisting of a fine dispersion of at least two mutually incompatiblepolymer materials (B) and (C), (B) being compatible with (A) and capableof adhering thereto, (C) being easily removable, and subjecting saidstrand, While still in a fluid or semi-fluid state, to simultaneousstretching and twisting.

In a preferred mode of carrying out the process, this comprises thesteps of mixing B and C at random to a fine dispersion, extruding saiddispersion through one channel system and A through another channelsystem, uniting the two polymer streams in a rotating nozzle adapted toapply the dispersion as coat on A, hauling off the composite filament bymeans not following the rotation of said nozzle, and cooling thefilament to solidification.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the structure of a yarnformed from the composite filament by removal of C, and

FIG. 2 shows a nozzle system suitable for producing the compositefilament.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the fibrous spongeor network formed material B being twisted around the core material A.The meshes of the network or sponge formed by- B may be very openbecause of the drawing-down of the core A.

In FIG. 2, 1 is the rotating nozzle part, 2 the steady part for feedingof polymer A, and 3 is the steady inlet part for the polymer dispersion(B-l-C). The bearings and transmission means for 1 are not shown.Polymer A is fed through a channel 4, which is connected to oneextruder, whereas the polymer dispersion is fed through channel 5connected to another extruder. Channel 5 widens out to a ring-formedchamber 6, which is in connection with a series of channels 7 arrangedin star-form in the rotating part. The dispersion is thus coated uponthe core material in the chamber 8.

During the passage through channels 5, 6, 7 and 8, the dispersion willbe strongly drawn and thus acquire a fibrelike structure in meltedstate.

The filament is hauled olf from the nozzle by rollers which do notfollow the rotation of 1, thus the structure of the stretched dispersionwill be arranged helically. Air cooling is applied to solidify thecomponent B of the dispersion immediately after the extrusion, and thecooling eiect is so controlled that the crystallization of B takes placewhen A has onlyl been stretched to a very small extent, whereas a deepdraw-down of the core A should be allowed after the crystallization ofB.

i EXAMPLE A is a copolymer between polyhexamine-adipamide andpolycaprolactam in a copolymerisation ratio of 40/ 60 (trade name Nylon6A). B is polycaprolactam homopolymer, and C is polyethylene. The meltindex of the copolymer is 2 according to ASTM No. 1238-57T condition K.The melt index of the homopolymer is 0.3 according to the same testingmethod, and the melt index of the polyethylene is 20 (same ASTM No. butCondition E).

The contents of polymer B is 30% of polymer A. The contents of polymer Cin the dispersion with A is 40% of the total amount of dispersion.

B and C are first dry-blended, then thoroughly mixed in a so-calledplanetary screw extruder from which the dispersion is directly fed tothe device shown in FIG. 2. The component A is fed to the dye by meansof a normal extruder.

The diameter of the orifices of the extruder is 0.5 mm. and the filamentis drawn down to a ydiameter of 0.08 mm., while the copolymer is stillmelted. The final product has a twist of about one rotation per cm.

The present invention can furthermore with advantage be carried out onother polymer combinations, e.g. with as the A component of polyurethanecopolymer of elastomer character, and as the B component a compatiblepolyurethane homopolymer.

I claim:

1. A process for producing a composite filament material comprising thesteps of providing a continuous strand of a filament forming polymermaterial (A), applying to the surface of said strand a substantiallycontinuous layer of a coating material consisting essentially of a finedispersion of at least two mutually incompatible fusable polymermaterials (B) and (C) in fused condition, said material (B) beingcompatible with said material (A) and capable of adhering thereto, saidmaterial (C) being easily removable from admixture with said material(B),

and subjecting said strand, while the coating material is still in afused state, to simultaneous stretching and twisting, and thereaftersolidifying the composite filament maf terial.

2. A process as in claim 1, in which the polymer materials (B) and (C)are so selected that (B) is capable of forming crystal whiskers.

3. A process as in claim 1, in which component (B) has a higher modulusof elasticity than component (A).

4. A process as in claim 1, in which said material (A) is a polyurethanecopolymer of elastomerY character and said material (B) is a compatiblepolyurethane homopolymer. u

5. The process of claim 1, wherein said filament forming polymermaterial (A) is fusable and is extruded in fused condition to form saidcontinuous strand, said layer of said coating material is applied whilesaid strand is being extruded, and both said strand and said layer ofsaid coating material are subjected to simultaneous stretching andtwisting while in said fused condition.

6. The process of claim 5, wherein the polymer material (A) has a lowermelt temperature than said polymer material (B) and after said material(B) is solidified but while said material (A) remains substantially insaid fused condition, said composite filament material is stronglystretched.

7. The process of claim 1 wherein the solidified composite filamentmaterial is treated to remove said polymer material (C) therefrom.

8. The process of claim 1 wherein said polymeric ma terial (A) is anelastomer.

9. The process of claim 1 wherein the diameter of said core issubstantially greater than the thickness of said layer applied thereto.

References Cited UNITED STATES PATENTS l 2,171,095 8/ 1939 Orsini 264-75X 2,174,779 10/ 1939 Delorme 264-75 lX 3,180,912 4/1965 Rowe 264-75 X3,279,501 10/ 1966 Donald 264--209 X 3,281,897 11/1966 Mercer 264-209 X3,415,919 12/1968 Kippan 264-174 X 3,461,197 8/1969 Lemelson 264-174X3,439,491 4/1969 Scruggs 57-144 X 3,446,002 5/1969 Kippan -..1.---57-144 X 2,904,846 9/ 195 9 Smith 264-174 3,310,505 3/1967 Parker et a126o-2.5 3,316,336 4/ 1967 Smith 264-171 3,382,305 5/1968 Breen 264-1713,416,982 12/ 1968 Petzetakis 264-171 3,455,773 7 1969 Tessier 264-493,475,898 11/1969 Magat et al. 161-180 3,479,419 1 l/ 1969 Hochhauser264-174 3,498,873 3/ 1970 Schrenk 264-171 3,565,985 3/1970 Schrenk264-171 JAY H. WOO, Primary Examiner U.S. Cl. X.R.

